Numerous techniques for holding ring binders in the closed position have been shown in prior patents (U.S. Pat. Nos. 1,927,113; 2,061,676; 3,098,490; and 3,101,719).
More recently, locking mechanisms as shown in U.S. Pat. Nos. 3,884,586 and 4,813,803 have been used to prevent inadvertent opening of ring binders when subjected to forces such as bumping or dropping of the binder.